docs: def print_summary(self):
          """
          print out stats about loading operation
          """
          if self.sources_valid:
              printDebug(
                  "----------\nLoaded %d triples.\n----------" % len(
                      self.rdflib_graph),
                  fg='white')
              printDebug(
                  "RDF sources loaded successfully: %d of %d." %
                  (len(self.sources_valid),
                   len(self.sources_valid) + len(self.sources_invalid)),
                  fg='green')
              for s in self.sources_valid:
                  printDebug("..... '" + s + "'", fg='white')
              printDebug("----------", fg='white')
          else:
              printDebug("Sorry - no valid RDF was found", fg='red')
  
          if self.sources_invalid:
              printDebug(
                  "----------\nRDF sources failed to load: %d.\n----------" %
                  (len(self.sources_invalid)),
                  fg='red')
              for s in self.sources_invalid:
                  printDebug("-> " + s, fg="red")